Fully acetylated sugar acid chlorides and process for their production



Patented Apr. 30, 1940 UNITED STATES PATENT OFFICE FULLY ACETYLATED SUGAR ACID CHLO:

RIDES AND PROCESS FOR THEIR PRO- DUCTION Jersey No Drawing. Application December 23, 1936,

Serial No. 117,336

6 Claims.

This invention relates to acetylated 2-ketosugar acids, and certain derivatives thereof, and to processes for their production.

The 2-keto-sugar acids have recently acquired 5 considerable interest in view of the fact that the enol forms of the lactones from these acids have been shown to be vitamin C and its homologs. (Hirst, Chemistry & Industry, 1933, p. 221, and I-Iaworth, Chemistry 81 Industry, 1933, 482.)

We have discovered a new method of preparing the acetyl derivatives of these acids, which involves the use of fully acetylated sugar acids as starting materials. These latter have been prepared by us for the first time, and are embraced in a patent application being filed concurrently herewith.

According to our improved process, the selected fully acetylated sugar acid is first converted to its acyl chloride. This latter is converted into the corresponding nitrile, from which the corresponding 2-keto acid may be obtained by hydrolysis. The acid thus obtained may be easily esterified.

We are attempting to hydrolyze the acetyl groups and enolize the keto group of pentaacetyl- Z-keto-glucoheptonic acid and its ester to give a homolog of vitamin C.

In the following examples, we are illustrating the steps of our process as applied specifically to pentaacetyl-d-gluconic acid and tetraacetyl-d,

l-xylonic acid:

FULLY Acnrm'rco SUGAR ACID CHLORIDES The dry fully acetylated sugar acid is added with cooling to a suspension of one molecular equivalent of phosphorus pentachloride in ten times its weight of dry ether. The reaction is soon completed, as shown by the disappearance of the phosphorous pentachloride.

Pentaacetyl-d-gluconyl chloride slight vacuum, beautiful white crystals separate.

They have a melting point of 68-70", and

e+2 (dry chloroform, c, 2). I

With water, the acid chloride gives pentaacetyld-gluconic acid monohydrate.

Tetraacetyl-d,1 -aaylonyl chloride (dry chloroform, c, 2). I

10 FULLY ACETYLA'I'ED 2-K1171o SUGAR A011) NITBILES Pentaacetyl-2-7ceto-d-glucoheptonitrile About 10 gms. of pentaacetylgluconyl chloride 5 are heated for one hour with 4.7 gms. of silver cyanide in a closed tube at -125 C. The fused contents are frequently shaken to insure good contact of the acid chloride with the silver cyanide. After cooling, the gummy material is 20 thoroughly extracted with anhydrous ether and filtered from the silver salts. Petroleum ether is added carefully to precipitate a part of the product as a dark colored syrup, thereby removing most of the color. Then an excess of petroleum 25 ether is added with cooling. A gum is precipitated along with some crystalline product. The supernatant liquor is poured off and on evaporation yields crystallinepentaacetyl-Z-keto-d-glucoheptonitrile. The gum is dissolved in a small quantity of absolute alcohol and upon standing in an ice box for 24 hours yields a quantity of pentaacetyl-Z-keto-glucoheptonitrile. The product is purified by recrystallizing it from absolute alcohol. It has a melting point of 116, and

(dry chloroform, c, 2).

When this compound is heated in water with 40 either dilute acid or a base, hydrogen cyanide is evolved.

Tetraacetyl-2-lceto-d,1-gulononitrile This nitrile is prepared in the same way as 45 pentaacetyl-2-ketod -glucoheptonitrile, except that the filtrate obtained after the addition of sufficient petroleum ether to the ether extract to produce slight turbidity, is treated with another larger portion of petroleum ether which precipitates a gum. Trituration of this gum with absolute alcohol yields a solid precipitate. It is recrystallized from alcohol, and has a melting point of -126". 55

FULLY ACETYLATED 2-KETO SUGAR AcIos Pentaacetyl-Z-keto-d-glucoheptonic acid About 7.55 gms. of pentaacetyl-Z-keto-d-glucoheptonitrile are'dissolved in '20 cc.--of pure dioxane. To this, about 13.1 cc. of 1.39 11 hydrogen chloride in dioxane is added. The solution is cooled and 0.33 cc. of water is added. The solu-."

tion is allowed to stand for another 24 hours, by which time ammonium'ichl'oride: precipitates. Ether is added and the ammonium chloride filtered. The filtrate is evaporated in vacuo to a gum. The gum is dissolvedfin'ether and evaporation in vacuo is repeated. *flfhe remaini g 'gum crystallizes on scratching. 7 It has a'inltihg point 0f-136-138". After recrystallization from Water it melts at 160-161,

(alcohol 0, 2). A solution of the keto acid in Water is acid to Congo red paper. I It is extremely soluble in alcohol;--ether, cliloroform, and acetone.

EsTERs 0F FULLY 2-KETO SUGAR-Acres Ethyl @entaacetyEZ-kto d-gilucoheiotondte A solution of 1 gm. of pentaacetyI- Z-ketO-dglucoheptonic acid in'lO cc. of absolute alcohol containing 2% hydrogen chloride is warmed at 60- for 5 minutes. The'solution is quickly cooled to nearly .room temperature and then allowed to crystallize. It has a melting point of 97-98;

"(alcohol c,2) i

Methyl t'etraacetyl-2 keto=d-gluconate About 1 gram of methyl 2-keto-d-gluconate is added to 5 "cc. of acetic anhydride containing 0.4 gm. of zinc chloride at 0. As soon as solution is complete (about 30 minutes) the mixture is allowed to come to room temperature and remain there for 24 hours. It is then poured into 25 cc. of ice water. A white solid separates. It is recrystallized from absolute alcohol and has a melting point of l68-l69 and "(chloroform 0,2).

From the foregoing description of the detailed steps of our new process, it will be apparent to those skilled in the art that tetraacetyl-Z-keto- 'd,1-xylonyl chloride which comprises t'reating dry tetraacetyl-d,1-.Xylonic acid with phosphorus pentachloride.

'5; In a process for the produc'tiorrof acetylated 2-keto-sugar acids from fully scammed sugar acids, the step "which comprises producing the corresponding acid chlorides by're acting upon the appropriate fully ac'etylateol sugar acid witliflphos- --phorus"pentachloride. I

6."Process for the production "of pentaa'c'etyb 'dgluc'onyl chloride which comprises reacting pentaacetyl-d-gluconic acid with phosphorus pentachloride.

' RANDOLPHTKMAJOR. v

I E-LMER COOK. 

